Sheet piles or piling for certain uses such as seawalls, for example, may be formed of interlocking sheet piling extruded from special vinyl formulations. Vinyl sheet piles are inert to a marine environment, will not deteriorate in fresh, brackish, or salt water applications, and will not leak harmful chemicals into the water or soil. Vinyl sheet piles are also resistant to marine borers, rot, rust, galvanic corrosion, and highly acidic or alkaline soil conditions. However, vinyl sheet piles or piling, like plastic piling and other piling formed of non-metallic material or relatively thin metal material such as aluminum, is particularly vulnerable to becoming damaged when driven into an earth formation.
Sheet piling is usually driven or inserted within the soil or earth formation by drop hammers or vibratory hammers. However, certain conditions, for example low temperatures at which vinyl sheet piling tends to be brittle, contribute to the vulnerability of the piling to possible damage during the process of driving the piling into the soil. Also some soils or earth formations are particularly resistant to sheet piling and effectively refuse penetration of the piling. Continued efforts to force the piling in such highly resistant soils can result in damage to the piling. Also, certain known apparatuses and methods believed generally effective for use in installing vinyl sheet piling can be less effective in certain soils due to sticking of the soil on the apparatuses.
U.S. Pat. No. 5,503,503, issued Apr. 2, 1996, teaches a protective housing or shield that protects sheet piling during driving or insertion of the sheet piling into soil or an earth formation. The protective housing or shield is preferably formed of metal having a cross section generally similar to the cross section of the sheet pile and adapted to be releasably connected to the sheet pile for simultaneous movement with the sheet pile. The protective housing is of a length greater than the length of the sheet piling and extends beyond the upper and lower ends of the sheet piling. The protective housing and connected sheet pile are driven downward into the formation together to a desired or predetermined depth. Then, the protective housing is lifted upwardly for removal or withdrawal leaving the sheet pile in place.
That is, after insertion of the sheet pile at the desired depth in the formation, the protective housing or shield is removed by lifting of the protective housing vertically relative to the sheet pile. While generally quite effective, the protective housing and sheet pile may sometimes adhere or stick to each other, and the protective housing may be difficult to break loose or separate initially from the sheet pile. Such sticking is typically most problematic in certain clay soils.
The natural resistance of soils to penetration of piles provides desirably tight holding of piles in an earth formation. However, when soils are so resistant or so compacted as to make driving piles extremely or even prohibitively difficult, the piles, although protected by the housing provided in U.S. Pat. No. 5,503,503, may still not be driven into the earth formation to the desired depth.
Conventional methods for reducing soil resistance at the time of driving steel pipe pile into the ground have included spraying water onto the pile surface before attempting insertion of the pile or jetting water into the ground from a jet pipe attached to the central tip of the pile during pile driving.
These conventional methods, however, are not always effective, especially with non-metal and thin metal piles. An especial problem with water jetting is weakening the ground with the large quantity of uncontrolled water injected, resulting in failure of the soil to tightly hold the pile as needed. For this reason, water jetting for piling has been disapproved by the United States Army Corps of Engineers and such jetting for piling is now prohibited in many if not all areas of the United States. A need in the pile driving industry continues to exist for improved methods and apparatuses for inserting non-metal and thin metal sheet piling into highly resistant earth formations.